This invention relates generally to a powder coating composition and, more specifically, to a thermosetting epoxy resin powder coating composition useful for application to slot insulation purposes.
There are known epoxy resin powder coating compositions useful for forming electrically insulating deposits or layers on electric or electronic parts. For example, Japanese published unexamined patent applications (Tokkyo Kokai) Nos. 55-84371 and 57-42760 disclose powder coating compositions containing an epoxy resin modified with a rubber, and a curing agent. While these powder compositions are effective for forming insulating deposits or layers on flat surfaces, they are ill-suited for the insulation of edge portions such as of slots of rotors or stators of electric motors. In particular, powder coating is generally performed at a temperature of 180.degree. C. or more so as to effect the coating within a short period of time. At such a temperature, sharp edge portions often failed to be coated with the conventional coating composition or, if coated, the coated layer is not satisfactory because it lacks resistance to heat, impact strength, surface smoothness or adhesion strength.